154 



THE AGRICULTURAL NEWS. 



May Ifi, 1908. 



INSECT NOTES. 



Flower-bud dropping of Cotton at Antigua. 



Early in the present year some cotton growers at 

 Anlis^iia, in going over their cotton fields, ol)served that 

 numbers of the Hower-bnds on the plants had dropped off 

 to the ground just at the period when they were about 

 to open into flower. The attention of the Imperial 

 Depart ment of Agriculture was called to tiiis occurrence, 

 and as it was believed that the trouble was due to some 

 insect pest, the Entomologist paid a short visit to 

 Antigua in Februaiy. Aitei' returning to Barbados for 

 a fortnight, a second vi.sit of a month's fluration was 

 made by Mi-. Ballon from March 6. During the fort- 

 nigiit's interval between the two visits, it was evident 

 that conditions had much improved, and many plants 

 which ])reviously had not a flower on them were reported 

 to be beginning to bloom freely. This improvement 

 continued throughout the second visit, and by ilie end 

 of March the ])est had practically disappeared, and the 

 flower-bud dropping had almost entirely ceased. 



The following forms the chief portion of a prelimin- 

 ary report furnished by Mr. Balloii on his investiga- 

 tions into the cause of the trouble, which he had 

 previously determined to be a small fly lielonging to 

 the natural ortler Diptern, and to the family ('eci- 

 domyiidae : — 



I devoted myself tn a study "f the insect, in order that 

 ] might get as much int'o_rniati')n us possible, and a few 

 ex[ierinients \\eve estaUislied. As a result of this study, it 

 ajijieais that the maggots leave the liud .soon after it falls, and 

 fft into tbi' ground to pupate. The pupa is naked, the pupal 

 eovering very thin and delicate, and pnitation is earned out 

 some 1 or 2 inches beneatli the surface. The dnnition of the 

 pupal stage is alxmt ten to foni-teen days. 



The flies live Lut a few days after reaching the adult 

 eondition. The female punctures the tis.suc of the bud with 

 tlie ovipositor, and inserts the eggs. I'robublj' .several 

 females lay their eggs in the .same bud. 1 have found as 

 many as forty-three maggots in one bud, and these of such 

 varying sizes as to indicate .several depositions of egijs. The 

 length of time taken foi' tlie eggs to hatch, and for ihr 

 magijots to become full-grown has not been a.scertained, tint 

 the indications are that it is very short, probably not nnicli 

 more for egjj;s and larval stages togethei' than is re(iinrcd for 

 the pupal stage. If this su|)position is correct, the total 

 length of time rec|uired lor the life cycle is about four weeks. 

 As stated in the report on my visit to Antigna in 

 February, most of the cotton planted jiievious to August !-"> 

 made a fairly good crop, while the gieater part of that planted 

 from September 1 did not give a croji. A few of the earliest 

 . blossoni-S on Septendier cotton escaped attack, and again 

 blo.ssonis escaped in early February. The former of these 

 gave a few liolls whicli wci-e ripening in March. The few 

 flowers uliieli esia| I d attack in I'Vbrnary resulted in bolls 

 vvliicli, at the lieginniiii.' of .\piil. had made good develo|inu'nt. 



The first imUcation of the presence of the disease in 

 Antigua was the excessive drop[iing of the buds. Then it 

 was "fciund that in the case of many of the buds the bracts, 

 instead of remaining clo.sed (adpres.sed) around the bud, had 

 tlared out in a strikuig manner, and on exanunation it was 

 found that all buds with ' tlared ' Israels were infested, and 

 I later discovered as the result of exanunation of large 

 numbers of buds that nearly all infested buds become ' tiared' 

 before dropping. 



The conditions which have led up to this remarkable 

 and very serious outbreak of this new pest can only be 

 surmised, but from the evidence at hand it would seem that 

 the surmise is well founded. 



In the first [)lace the pest is proluibly a native of 

 Antigua, or at lea.st not a recent iniiiortation. This is l)orne 

 out by the fact that it apiteared in all parts of the island 

 almost simultaneously and with a uniform degree of severity. 

 The Hy is very fragile and probalily not capable of any long 

 fiight, nor ft being carried far by the wind. Secondly, the 

 weather conditions in Antigua have been rather unusual for the 

 past eighteen months. Begiiuiing with the very heavy rainfall 

 of September 1900, Antigua has experienced wet and damp 

 weather in rather an unusaal degree in many [larts, without 

 perhaps recording a rainfall nuicli, if any. above the average. 

 This ilampness, with the stronger growth of the plants, the 

 nifiister soil, and the great tendency to weeds in the fields, 

 gave the maggots as they fell to the ground a better oppor- 

 tunity of pui)ating than luider the normal conditions in 

 Antiijua. It was noticed on several estates that cotton fields 

 in wiiich there was a tendency to damp soil, and where a strong, 

 vigorous growth of plants covered the ground, were more 

 .severely attacked than the fields in which the .soil was drier 

 and the plants siiialler. When, as sometimes happened, 

 there was a strong tendency tow-ard a rapid growth of weeds 

 on the damp .soils, the difference was still more noticeable. 

 Two small insects which belong to the parasitic 

 Hymenoptera were very common in all infested cotton fields. 

 One of these I found to lie a \ery active enemy of the 

 maggot in the Hower hud, an<l I believe the other to be the 

 .same, but 1 have nfit yet proved this point. 



It is likely that thi' sudden improvement in the condi- 

 ti(jn of the cotton fields and the almost total disappearance of 

 the magi;ots are due to the drier weather, ami hot briirht suns 

 of February, toj;ether with the beneficial etl'ects of tlu' 

 |iarasitic enemies of the maggots. 



I'p to the present time no reineilial measures have given 

 definite residt.s. Kx|)eriinents have been started and it is hoiied 

 that they may gi\e results that will be useful. The use of 

 Vaporite seemed likely to be beneficial, and .several ai)plica- 

 tions of this material have been made. \'aporite is a proprie- 

 tary material sold by Straw.sons A" Co., England. Its object 

 is the killing of in.sects in the soil, and it was ho|)ed that 

 during the time when the maggots and the pupae were in the 

 soil, the ert'ect of the Vaporite funics wimld be sntficient to 

 kill most of these insects. 



('nitural nietliods may i-eiliice tlic loss from this form of 

 Moucr-bud dropping. Any system of planting anil tillage 

 which allows the sun to get freely to the ground around the 

 plants, and whicli kee]is the surface thoriaighly pulverized, 

 dry, and free from weeds, udidd seem likely to be useful. 

 Wet weather, damp surface soil, and the presence of weeds, 

 seem to be favoural>le to the increase i^f llie pest. 



The insect which causes this dropiang of llower buds of 

 cotton has recently been determined, by Dr. E. P. Felt, New 

 ^'ork State Kntomdlogist, to be a new species of the genus 

 Ciiiitiirinid, and lie pro|iosed to give it the name Conturinin 

 .jaxxi/ini. 



